This invention relates generally to electrostatorgraphic apparatus and, more particularly, to radiant energy apparatus for fixing toner images to a support member.
In the process of electrostatography, latent electrostatic images are formed on a support member, for example, plain paper with the subsequent rendering of the latent images visible by the application of electroscopic marking particles, commonly referred to as toner. The toner or powder images so formed vary in density in accordance with the magnitude of electrostatic charges forming the individual images.
The toner images can be fixed directly upon the support member on which they are formed or they may be transferred to another support member with subsequent fixing of the images thereto.
Fixing of toner images can be accomplished by various methods one of which is by the employment of thermal energy. In order to permanently fix or fuse toner images onto a support member by means of thermal energy it is necessary to elevate the temperature of the toner material to a point at which the constituents of the toner coalesce and become tacky or melt. This action causes the toner to be absorbed to some extent into the fibers of the paper. Thereafter as the toner cools, solidification of the toner material occurs causing it to be firmly bonded to the support member. In the process of electrostatography, the use of thermal energy for fixing toner images is old and well known.
One approach to thermal fusing of toner images onto a support member is to pass the support with the toner images thereon past a source of radiant energy such that the image bearing side of the support is opposite the source of radiation while the reverse side thereof is moved in contact with a support platen.
In order to be totally acceptable, a radiant fuser, for use in the type of apparatus contemplated, requires a wide fuse-scorch latitude. In other words, it should be capable of fusing high density images without scorching light weight (i.e. less than 20lbs. - basis weight 2000 sheets) copy paper and it should be capable of fusing low density images without fusing background toner particles. It should also be capable of rapid warm-up.
Prior attempts at meeting all the foregoing requirements in a single radiant fuser have been unsuccessful.
Accordingly, it is the primary object of this invention to provide a new and improved radiant fuser for use in an electrostatographic apparatus.
It is a more particular object of this invention to provide, in a xerographic reproducing apparatus, a radiant fuser having a wide fuse-scorch latitude which also has a short warm-up time.
Another object of this invention is to provide a new and improved radiant fuser having plural energy sources one of which comprises a quartz lamp radiating short wavelength energy readily absorbed by toner and the other of which comprises a low mass element capable of radiating long wavelength energy which is readily absorbed by the copy paper.